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How to Install Neutralization Tanks

Buried Tank Installation

Tanks must be fully supported on the base by either an appropriate concrete pad that allows no overhang or a compacted stone-free sand bed.

When buried, tanks must be filled with water prior to backfilling. Tank tops are non-load bearing and should have a trap door or access cover over them supported by a foundation or by the ground. They cannot be supported by the top of the tank.

The backfill material shall be free of stones and foreign matter and shall be capable of passing a No. 10 screen. The depth of this backfill should be 6" to 8" thick around the tank and then normal backfill material may be used. Mechanical tamping is not recommended. For tanks with extensions, the above procedure should be followed up to or slightly above water level and from that point on up to ground level it is recommended that a 4" thick concrete sleeve be poured around the tank in multiple lifts. If this is not feasible then the normal backfill procedure may be used, up to 36" height above water level, bearing in mind that backfilling will produce inward pressures on the empty portion of the tank. Care must be exercised during this operation to prevent inward buckling.

A concrete vault must be used or a 4" thick concrete sleeve poured around the tank in multiple lifts in areas with high water tables or poor soil conditions. If the tank is to be used as a pump-out holding tank or similar type of operation or the tank will be left empty or partially full, then a vault is required.

We recommend:

Tanks that are going to be direct buried be fiberglass wrapped.

Limestone Usage

Limestone chips are being used in numerous applications to help neutralize chemical bearing wastes (e.g. acid wastes). After years of successful neutralization, many states and local environmental plumbing codes call for the addition of limestone chips into acid neutralization basins, tanks, or sumps. Water is added to the tanks to initiate the dilution process.

We recommend:

Limestone chips be one to three inches in diameter size range and have a calcium carbonate content in excess of 90%.


Our neutralization tanks must not be pressure tested. Test tank by filling with water prior to use and inspect for any leaks.


The limestone supplied by Orion are 1-3" in diameter and have a calcium carbonate content certified to be in excess of 90%. Waste is added to the tank to help facilitate dilution. A maintenance schedule should be established to observe and maintain proper limestone levels in the tank. Limestone replacement should be performed at regular intervals. Typically, once every one to three months is sufficient, however, these intervals can be increased of decreased based upon application needs and performance. Factors affecting limestone replacement are waste flow rated and chemical composition as well as operating temperatures. Solids in the waste stream can plug the tank and should be avoided.

*Note: There are many variables that affect neutralization and dilution of chemicals discharged through a system. Professional assistance should be employed in analyzing the effluent and the necessary maintenance service.